The Hubble Space Telescope’s Finest Photos

In April 1990, a tin can the size of a school bus was dropped off 353 miles above the Earth’s surface. Its mission: Take clear pictures of the universe without interference from the planet’s atmosphere. Nineteen years later, NASA’s Hubble Space Telescope has transmitted hundreds of thousands of spectacular images to astronomers back home. From far-away stars and neighboring planets to evidence of dark matter and the precise age of the universe, these photographs have allowed us to see what once existed only in scientists' computations.

One of Hubble’s first victories was capturing several embryonic stars or EGGs (evaporating gaseous globules) hiding throughout clouds in the Eagle Nebula. Within these finger-shaped clouds, nicknamed the “pillars of creation,” molecules of gases such as hydrogen and helium clump together and begin to generate their own gravity, which draws in nearby gas and dust. If these balls of gravity grow big enough, nuclear fusion reactions will be triggered in their cores, and they will become stars.

On July 4, 1054, a “new star” startled Chinese astronomers, who wrote that the star was so bright that it was visible in broad daylight for several weeks. Almost a thousand years later, we know that the appearance was caused by a star 10 times the mass of our sun that exploded as a supernova. What’s left of the dead star is still spewing out high-energy particles into the Crab Nebula. This Hubble image, composed from 24 exposures, reveals the nebula’s structure.

What kind of star died on October 9, 1604? On that day, several observers spotted a supernova that was as bright as Mars. German astronomer Johannes Kepler was so taken with the sight that he wrote a book about it. Kepler’s supernova is thought to be the most recent star to explode in our Milky Way galaxy. Astronomers combined the forces of the Hubble, Spitzer Space Telescope, and the Chandra X-ray Observatory to see if they could identify the type of star that produced the explosion; they could not. But this rainbow photograph of the supernova remnant combines all the images. The different colors represent infrared radiation (red), visible light (yellow), and X-rays (blue/green).

These white dwarf stars, located 5,600 light-years away in the constellation Scorpius, are the dimmest and oldest stars in our Milky Way, still cooling after a 12-billion to 13-billion-year existence. White dwarfs cool off at a predictable rate, so scientists can tell a star’s age from its brightness. If, as astronomers theorize, the first stars formed less than 1 billion years after the universe’s birth, these stars clock the universe at 13 billion to 14 billion years old. Astronomers had already calculated this age in 1997, based on the rate at which the universe is expanding. The Hubble photographs verified that their math was correct.

Hubble’s face-on view of this unusual galaxy, known as Hoag’s Object after Arthur Allen Hoag, who discovered it in 1950, shows its nearly perfect ring of hot, massive, blue stars surrounding a nucleus of older, yellow stars. Ring-shaped galaxies can form either through a collision with another galaxy or when a second galaxy speeds through the first, leaving parts of itself behind. In Hoag's Object, there is evidence that the blue ring may be the shredded remains of a galaxy that passed nearby. Astronomers estimate that the encounter occurred 2 billion to 3 billion years ago.

This detailed Hubble image of the Cat's Eye Nebula, discovered in 1786, reveals a bull's eye pattern of at least eleven concentric rings around the nebula’s glowing nucleus, a dying Sun-like star. Each 'ring' represents a spherical layer of gas and dust ejected by the star, an event that occurs in 1,500-year intervals. Why this happens is unknown. Some astronomers think that the pulses may occur in sync with the star’s magnetic activity or with the gravitational pull of stars orbiting nearby.

Hubble’s photographs don't appear fully formed and ready to be saved as desktop backgrounds. A team of astronomers and image specialists, known as the Hubble Heritage Project, were required to create the final image of the Sombrero Galaxy above. The photo, which resembles the rim and bulge of a sombrero, reveals a flat disk of young, bright stars, orbiting around a glowing nucleus of more stars. A supermassive black hole lies in the center of the galaxy, which is located in the constellation Virgo.

The light from a distant sun can take thousands of years to reach Earth. Looking at the night sky is like watching ghosts—some of the stars may have burnt out long ago. In 2004, Hubble captured a light burst from the star V838 Monocerotis, a red supergiant on the outer edge of our Milky Way. The light pulse, which illuminates the dust clouds surrounding the star, took place 20,000 years ago.

Hubble sees the universe through Earth’s eyes. Our view of other planets, for instance, is limited by which side is tilted toward our planet on a given night. To get a full glimpse of Saturn, Hubble joined forces with NASA’s Cassini orbiter, on the far side of the gas giant, to snap three-dimensional pictures of the planet and its rings. For the first time, astronomers were able to compare views of Saturn of equal sharpness from two very different perspectives. The colors in the photograph resemble what the planet would look like to the human eye.

This picture of the pinwheel-like galaxy NGC 1309 helped astronomers more accurately measure the universe’s rate of expansion, original discovered in 1929 by Edwin Hubble, the space telescope’s namesake. By measuring supernova explosions, scientists have been able to determine that this expansion is accelerating, because galaxies like NGC 1309 are moving away ever faster.

The Earth’s gravitational pull is strong enough to hold its atmosphere and moon in place. The Sun’s gravity draws together the eight planets and numerous asteroids. But that’s nothing compared to the pull of a black hole, which is so powerful that light cannot escape. A black hole exists in the heart of our galaxy, and possibly all galaxies. This Hubble photograph shows dozens of galaxies bound together by the gravity of a supermassive black hole famous among astronomers for generating the most powerful outburst seen in the universe.

When scientists reserve time to use the Hubble, they can point the telescope in almost any direction, even toward our own neighborhood. In 2006, Hubble was used to photograph a disintegrating comet called Schwassmann-Wachmann 3, discovered in 1930. Every 16 years, the comet flies near Earth, leaving a trail of dust and ice in its wake. The Hubble pictures show several dozen "mini-comets” trailing behind the eight main fragments. The comet is falling apart in house-size chunks due to the heat and gravity of the Sun.

During its seven-day orbit, Jupiter’s moon Ganymede ducks behind its host planet and hides from astronomers on Earth. Though a speck next to the gas giant, Ganymede is our solar system’s largest moon, larger than the planet Mercury. It is made of rock and ice, and has noticeable impact craters. Visible in this natural-color Hubble image is Ganymede’s surface as well as Jupiter's Great Red Spot, a storm the size of two Earths that has been raging for more than 300 years.

Nobody even knew Uranus had rings until 1977, when a team of American astronomers observed the planet as it passed in front of a star. Hubble’s photographs of Uranus’ rings contributed to our knowledge of how many exist, 13 as of 2008. In this image, the rings appear as two spikes above and below the planet. Earthbound astronomers see the rings' edge only every 42 years as the planet follows an 84-year orbit about the Sun.

Every 26 months, Mars and Earth have a close encounter. Earth travels around the Sun twice as fast as Mars and since both planets have an elliptical orbit, these encounters differ in distance each time. Hubble caught the red planet on one of these fly bys, when Mars was just 55 million miles away. This color image taken within 36 hours of the approach shows Mars free of any dust storms, but with noticeable cloud cover in both the Northern and Southern hemispheres.